1. Field of the Invention
The present invention relates to a content receiver, a license server, a content utilization system, a content viewing time limit management method, and the like for copying and bringing out an encrypted content with managed viewing time limit from a content receiver to an exchangeable medium to reproduce the encrypted content by a reproducer.
2. Related Art of the Invention
In recent years, owing to the development of the Internet, techniques for downloading and reproducing movies, music, and the like are generally used. A large number of services are provided for downloading, through networks, contents from servers, which perform content delivery of movies, music, and the like, to PCs, AV apparatuses, cellular phones, and portable apparatuses.
In such content delivery services, there are content sales of a sell-off type with which a user can permanently view purchased content and rental sales with which a user can view downloaded content within a limited viewing expiration time.
In typical content sales of a download type, a content provider which supplies content operates a content server and a DRM server, and a content receiver on a viewer side downloads an encrypted rental content from the content server and acquires, from the DRM server, a decryption key for the encrypted content and viewing conditions for the content. The viewing conditions for the content include information concerning a viewing expiration time within which a user is permitted to view the content and a copy condition for the content.
When the content receiver reproduces the rental content, the content receiver refers to a viewing expiration time designated from the DRM server. If the viewing expiration time has not expired, the content receiver starts reproduction of the content and, if the viewing expiration time has expired, the content receiver carries out deletion of the content.
In some cases, the content receiver writes out a rental content to an exchangeable medium such as an SD card together with the viewing expiration time. In this case, when a reproduction terminal for the SD card starts to reproduce a rental content or has ended the reproduction of the content, the reproduction terminal checks the viewing expiration time for the content, and deletes the content if the viewing expiration time has expired. As a method of reproducing content with viewing period of this type, for example, there is a method described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-227282).
FIG. 10 is a sequence diagram for a terminal that has downloaded a content from a server and moves the content so that the content is viewed in another terminal in conventional content downloading as described in Patent Document 1.
A download terminal 601 can view a content by storing the content distributed from a server 600 and acquiring a viewing license of the content from the server 600.
To allow the content to be viewed in another viewing terminal 602, the content can be moved from the download terminal 601 to the viewing terminal 602. However, the server 600 manages the viewing license in association with the download terminal 601. Therefore, the viewing terminal 602, which is another terminal, must acquire a viewing license by itself from the server 600 to view the content.
Regarding the forms of the viewing license to be provided, there are (i) a viewing license with viewing time limit for providing a reproduction permission condition of the target content by designating absolute date and time, and (ii) a viewing license with viewing term such that absolute date and time is not designated when the license is provided and only a viewable period, such as 48 hours, is designated for determining the viewing time limit upon the first viewing on the terminal.
Regarding the forms of selling a rental content, there is what is called pack selling. The pack selling provides, for example, all twelve episodes of a TV drama as one content group, or as a package, where the twelve episodes are provided at a lower price than the episodes to be individually purchased.
In this case, the price for the service paid by the user to the service provider is lower. But the viewing time limits of all the pack contents are usually unified. Specifically, in a case where the viewing license with viewing term is acquired at the time of the download of the contents, the viewing time limits of all twelve contents are set to the same date and time when viewing of any one of the contents is started after the download of the twelve contents.
However, in the above conventional technique, there is a problem that the viewing time limits of the contents cannot be unified as to a terminal that has written out the contents and a portable terminal when the rental content is written out, without a determined viewing time limit, to an exchangeable medium such as an SD card to be viewed by the portable terminal and the like.
This problem will be described below.
FIG. 11 is a sequence diagram for a terminal that has downloaded a content from a server to copy the content so that the content is viewed in another terminal in conventional content downloading.
When the download terminal 601 has never reproduced the stored content yet, which has been distributed from the server 600, and the content is brought out by copying to the SD card or the like, the viewing time limit of the content recorded in the SD card is not determined yet. Therefore, when the viewing terminal 602 starts to reproduce the content recorded in the SD card, the time limit of the content recorded in the SD card is determined.
On the other hand, in a case in which a content stored in the HDD in the download terminal 601 is viewed for the first time at the download terminal 601, the viewing time limit of the content stored in the HDD is determined when the first viewing is started.
With regard to the same content, because the time point at which the viewing of the content is started at the download terminal 601 differs from the time point at which the viewing of the content is started at the viewing terminal 602, the viewing time limit of the content stored in the HDD in the download terminal 601 differs from the viewing time limit of the content recorded in the SD card.
When some contents of the pack contents are brought by recording in the exchangeable medium, a similar problem occurs such that the viewing time limits differ as to contents in the same pack.
FIG. 12 is a sequence diagram, in which the download terminal 601 that has received pack rental content from the server 600 writes out some of the contents of the pack to an SD card 606, and the viewing terminal 602 starts to view the content on the SD card 606.
An HDD 605 of the server 600 stores twelve contents with content numbers 1 to 12 in a pack. A case will be considered in which the download terminal 601 downloads nine contents with content numbers 1 to 9 of the twelve contents and writes out (moves) five contents with content numbers 1 to 5 to the SD card 606.
If none of the contents with content numbers 1 to 9 has been viewed in the download terminal 601 before the contents are written out to the SD card 606, the viewing time limits of all contents with content numbers 1 to 12 are not determined yet and, for example, a viewing term is only designated e.g., the contents can be viewed during 48 hours from the first viewing. When any of the contents with content numbers 6 to 9, which are left in the download terminal 601, is viewed at the download terminal 601, it is decided that the period for the viewing time limit of the content is 48 hours from that time. Therefore, the viewing time limits of all contents with content numbers 1 to 12 need to be determined so as to be synchronous with the content.
However, the contents with content numbers 1 to 5 that have been brought out by the SD card 606 are under the management of the viewing terminal 602, and the download terminal 601 has no means to determine the viewing time limits of the contents with content numbers 1 to 5. The download terminal 601 also has no means to determine the viewing time limits of the contents with content numbers 10 to 12 that are not yet downloaded to the download terminal 601.
After that, when any of the contents with content numbers 1 to 5 in the SD card 606 is viewed at the viewing terminal 602, it is decided that the period for the viewing time limit of the content is 48 hours from the time of the viewing start in the viewing terminal 602. Consequently, this determined time limit differs from the time limit of the content (the above content of the contents with content numbers 6 to 9) which has been already viewed at the download terminal 601.
In consideration of the above-described conventional problems, an object of the present invention is to provide a content receiver, a license server, a content utilization system, a content viewing time limit management method, and the like capable of synchronizing viewing time limits of a plurality of contents even if some of the plurality of contents that need to have the same viewing time limits are written out to an exchangeable medium before the viewing time limits are determined.